A display device having a plurality of pixels (or sub-pixels) arranged in a matrix has been widely used in various applications. Such a display device includes a panel having the pixels and peripheral circuits for controlling the panels. Typically, the pixels are defined by the intersections of scan lines and data lines, and the peripheral circuits include a gate driver for scanning the scan lines and a source driver for supplying image data to the data lines. The source driver may include a gamma correction circuit for controlling the gray scale of each pixel. In order to display a frame, the source driver and the gate driver respectively provide a data signal and a scan signal to the corresponding data line and the corresponding scan line. As a result, each pixel will display a predetermined brightness and color.
In recent years, the matrix display using organic light emitting devices (OLED) has been widely employed in small electronic devices, such as handheld devices, cellular phones, personal digital assistants (PDAs), and cameras because of the generally lower power consumed by such devices. However, the quality of output in an OLED based pixel is affected by the properties of a drive transistor that is typically fabricated from amorphous or poly silicon as well as the OLED itself. In particular, threshold voltage and mobility of the transistor tend to change as the pixel ages. Moreover, the performance of the drive transistor may be effected by temperature. In order to maintain image quality, these parameters must be compensated for by adjusting the programming voltage to pixels. Compensation via changing the programming voltage is more effective when a higher level of programming voltage and therefore higher luminance is produced by the OLED based pixels. However, luminance levels are largely dictated by the level of brightness for the image data to a pixel, and the desired higher levels of luminance for more effective compensation may not be achievable while within the parameters of the image data.